This invention relates generally to artificial intraocular lens for replacing the natural lens of the eye, and more particularly to a novel intraocular lens which is capable of emulating the natural process of accommodation in direct response to contraction and relaxation of the ciliary body of the host eye.
Accommodation is the natural process by which the lens of the eye can sharpen the curvature of its front and back surfaces and thereby change its refractive power in order to adjust from distance vision to near vision. This occurs in response to contraction of the ciliary body which results in an approximate one-half millimeter decrease in the equatorial diameter of the lens capsule. A recent article, "How the Human Eye Focuses" appearing in the July, 1988 issue of the magazine Scientific American, describes very well the structure of the eye and the accommodation process.
Most conventional intraocular lenses have a predetermined fixed refractive power with no accommodation capability. Prior proposals intended to provide the accommodation function are illustrated in U.S. Pat. Nos. 4,373,218, 4,409,691, and 4,731,078, but these are rather complicated in construction and operation.
In addition, conventional intraocular lenses exhibit positioning instability in the eye, called decentration. These lenses decenter because the haptic fingers which support the lens from the ciliary body or lens capsule have very small surface areas in contact with these tissues. Small surface areas greatly increase pressure of the fingers against these tissues, thus making it difficult to maintain the lens in its centered position.
Another problem associated with conventional intraocular lenses is the introduction of significant amounts of glare or halo effects around images, especially in dim lighting situations when the pupillary aperture is large.